1. Field of the Invention
The present invention relates to a panel-type input device. The present invention also relates to a method of manufacturing a panel-type input device. The present invention further relates to an electronic apparatus having a panel-type input device.
2. Description of the Related Art
A panel-type input device has been known as an input device (or a coordinates detecting device) of an electronic apparatus including a display unit, such as a personal computer, a personal digital assistant (PDA), an automatic teller machine (ATM), etc., which is operated to indicate two-dimensional coordinate data in the display unit by an operator touching a desired point on a panel surface with his or her finger or with a pen. In particular, a panel-type input device with a transparent structure which can be mounted on a screen of a display unit, such as a liquid crystal display (LCD), a plasma display panel (PDP), a cathode ray tube (CRT), etc., has been widely used as a so-called touch panel, and in recent years, has been realized as an input device to be installed in a portable terminal unit having a mobile-phone function.
A resistive-type touch panel, as one example of a panel-type input device, includes a pair of transparent electrode plates, each having a transparent insulating substrate and a transparent conductive coat provided on one surface of the substrate, and has a configuration wherein the electrode plates are assembled with each other in such a relative arrangement that the conductive coats are opposed to and spaced from each other while permitting a conductive contact therebetween. As input-coordinates detection systems provided for the resistive-type touch panel, an analog system in which the conductive coat of each electrode plate is configured to be uniformly formed over the generally entire surface of the substrate, and a digital system in which the conductive coat of each electrode plate is configured to be divided into a plurality of strip-shaped portions on the surface of the substrate, have been known.
In the analog system, each electrode plate is generally provided, in a region extending along an outer edge of the electrode plate, with a pair of positive and negative strip-shaped electrodes (hereinafter referred generically as a parallel electrode pair) formed on the conductive coat so as to be parallel to and spaced from each other, and conductors are formed on an insulating layer on the conductive coat so as to be connected to the parallel electrode pair. Voltages are applied to the conductive coats of the mutually opposing electrode plates, via the conductors and the parallel electrode pairs, in directions orthogonal to each other. In this state, when an operator presses a desired point of one of the electrode plates (i.e., performs a touch input) so as to make the conductive coats of the mutually opposing electrode plates come into local conductive contact with each other, a divided voltage corresponding to the resistance value of the respective conductive coats is measured at the pressed point, and a coordinate of the pressed point is thereby detected.
In the digital system, a pair of electrode plates are combined with each other and positioned relative to each other in such a manner that the respective sets of strip-shaped portions of the respective conductive coats extend in directions orthogonal to each other. Voltages are applied to the sets of strip-shaped portions of the respective conductive coats of the mutually opposing electrode plates, and when an operator presses a desired point of one of the electrode plates (i.e., performs a touch input) so as to make the strip-shaped portions of the conductive coats of the mutually opposing electrode plates come into conductive contact with each other at the intersection thereof, the input operation at the intersection is detected.
A capacitive-type touch panel, as another example of a panel-type input device, includes a transparent electrode plate having a transparent insulating substrate and a transparent conductive coat provided on one surface of the substrate. As input-coordinates detection systems provided for the capacitive-type touch panel, a surface capacitive system in which the conductive coat of the electrode plate is configured to be uniformly formed over the generally entire surface of the substrate, and a projected capacitive system in which the conductive coat of the electrode plate is configured to be divided into a plurality of strip-shaped portions on the surface of the substrate, have been known.
In the surface capacitive system, the touch panel is essentially constructed by using only a single electrode plate. A uniform electric potential is given to the conductive coat by electrodes provided at four corners of the conductive coat. When an operator touches a desired point of the electrode plate (i.e., performs a touch input) with a finger, an electric current is generated at the touched point, and a coordinate of the touched point is detected based on the ratio between current values obtained at the four corner electrodes.
In the projected capacitive system, the touch panel is constructed by using a single electrode plate or a pair of opposing electrode plates, in which a pair of conductive coats, each being divided into a plurality of strip-shaped portions, are disposed on the opposite surfaces of the single electrode plate or on the mutually opposing surfaces of the opposing electrode plates, in such a manner that the conductive coats are opposed to and insulated from each other and the respective sets of strip-shaped portions of the conductive coats extend in directions orthogonal to each other. Voltage is applied to the respective sets of strip-shaped portions of the conductive coats. When an operator touches a desired point of the electrode plate (i.e., performs a touch input) with a finger, an electric current is generated at the touched point, or an electrostatic capacity between the mutually opposing conductive coats changes at the touched point, and a coordinate of the touched point is detected based on the locations of the strip-shaped portions generating electric currents correspondingly to distances from the touched point.
In a conventional panel-type input device as described above, the conductive coat is generally formed on the surface of the substrate by a coat-forming technology, such as vacuum deposition, sputtering, etc., using a metal oxide such as an indium tin oxide (ITO). On the other hand, in recent years, a panel-type input device provided with a conductive coat formed from an electrically conductive polymer (hereinafter referred to as a conducting polymer) has been proposed. For example, Japanese Unexamined Patent Publication (Kokai) No. 2005-182737 (JP-A-2005-182737) discloses an analog-system based resistive-type touch panel provided with a conductive coat formed from a transparent conducting polymer. Japanese Unexamined Patent Publication (Kokai) No. 2005-527048 (JP-A-2005-527048) also discloses a capacitive-type touch panel provided with a conductive coat formed from a transparent conducting polymer. JP-A-2005-527048 discloses both a surface capacitive system and a projected capacitive system. In any of the conventional panel-type input devices, the conductive coat formed from the conducting polymer has advantages, as compared to an ITO coat, in that the conducting polymer is excellent in impact resistance, writing durability, etc., and can be formed by a simple process such as coating or printing.
As described above, a conventional panel-type input device is provided, in connection with the conductive coat formed on the surface of the substrate, with an electrically insulating region having a predetermined profile formed on the surface of the same substrate or on the surface of the conductive coat. For example, in an analog-system based resistive-type touch panel, an insulating layer having a predetermined profile, on which conductors or connectors connected to the parallel electrode pair are disposed, is formed on the conductive coat along the outer edge of the substrate by, e.g., coating or printing. Alternatively, an insulating region for disposing conductors or connectors may be formed along the outer edge of the substrate by locally removing a part of the conductive coat through etching or the like. In a digital-system based resistive-type touch panel, or a projected-capacitive-system based capacitive-type touch panel, a plurality of strip-shaped portions of the conductive coat as well as an insulating region insulating the strip-shaped portions from each other are formed by locally removing, through etching or the like, a part of the conductive coat uniformly formed on the surface of the substrate.
The process for forming the insulating layer on the conductive coat through coating or printing requires a material for the insulating layer, and increases the entire thickness of the panel-type input device due to the thickness of the insulating layer. On the other hand, the process for forming the insulating region by locally removing the conductive coat through etching or the like requires the provision of a coating removing apparatus such as etching equipment and the increased number of processing steps, which may raise the manufacturing cost of the panel-type input device. In particular, in a touch panel adapted to be mounted on a screen of a display unit and configured such that the insulating region formed by locally removing the conductive coat exists within an area superimposed on the screen, the difference of the thickness or light transmission between the strip-shaped portion (i.e., a detecting area) and the insulating region (i.e., an inoperative area) may allow a boundary line between the strip-shaped portion and the insulating region to be visible or the detecting area and the inoperative area to be visually distinguishable, which may degrade the visibility of the display screen through the touch panel.